Cooling chamber design



J. E. LOEFFLER, JR., ETAL Nov. 15, 1966 COOLING CHAMBER DESIGN Filed Dec. 27, 1963 I 2 Sheets-Sheet 1 T RL N m mm A T. NET-K DR N EUSO D A V U w cm mmA c v Q M MMDH Q L M J HD dz a;

Fig.1

A QUADRANT QUADRANT 1966 J. E. LOEFFLER, JR.. ETAL 3,285,707

COOLING CHAMBER DESIGN 2 Sheets-Sheet 2 Filed Dec. 27, 1963 m Qk @N R E RL mwmm W NETK E W v U m United States Patent 3,285,707 COOLING CHAMBER DESIGN John Edward Loeflier, Jr., Lyndhurst, Ohio, and H. P.

McAlister, Houston, and Paul Revere Prokish, La Porte,

Tex., assignors to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware Filed Dec. 27, 1963, Ser. No. 333,896 3 Claims. (Cl. 23-277) This invention relates to improvements in apparatus for the production of unsaturated hydrocarbons by the incomplete oxidation of more saturated hydrocarbons, with oxygen, in a flame reaction, and more particularly relates to improvements in the type of apparatus for the production of such unsaturated hydrocarbons wherein the apparatus includes a mixing chamber for preheated streams of gaseous hydrocarbons and oxygen, a flame chamber into which a plurality of auxiliary streams of oxygen are introduced in order to stabilize the flame which is a source of energy for the reaction, and an intermediate section which may be regarded as a gas-distributor, flame-arrester, connecting the flame chamber and the mixing chamber. Still more particularly the invention relates to improvements in apparatus of the abovedescribed type wherein there is provided in the gas-distributor, flame-arrester, section a plurality of regularly spaced groups of symmetrically arranged tubular channels opening into the mixing chamber and the flame chamber.

According to methods well known in the art, unsaturated hydrocarbons may be produced by the incomplete oxidation, of more saturated hydrocarbons, with oxygen, in a flame reaction, the most notable of which is the production of acetylene from methane or higher hydrocarbons. Probably the most Widely used method involves the incomplete oxidation of methane with oxygen, by separately preheating methane and oxygen, mixing them as quickly and completely as possible in a suitable mixing chamber, the amount of oxygen used ordinarily being about one-third the stoichiometric amount for complete combustion to carbon dioxide and water, and passing the gas mixture through a gasdistributor, flame-arrester, section leading from the mixing chamber into the flame chamber. The gasdistributor, flame-arrester, section is customarily constituted by a cylindrical ceramic burner block in which there are regularly spaced, symmetrically arranged, tubular channels through which the gas mixture passes from the. mixing chamber to the flame chamber at a speed generally in excess of that at which flame propagation of the mixture of the hydrocarbon and oxygen will take place.

However, such an arrangement for the incomplete combustion of a hydrocarbon, and particularly methane, with oxygen, has two rather serious drawbacks, the first of which is the formation of relatively large amounts of carbon which are deposited upon the surface of the gas-distributor, flame-arrester, section facing the flame chamber and adjacent surfaces, thus not only diminishing the yield of acetylene, but when formed under the conditions existing in the reaction chamber, such deposits adhere very firmly, and must be removed by mechanical means. In such circumstance the face of the gasdistributor, flame-arrester, section may often be badly damaged and become unfit for further use within a short time. The second of these drawbacks is the matter of providing a stable flame in the flame chamber, i.e., a flame which retains its position in the flame chamber without fluctuation either away from or back toward the gas-distributor, flame-arrester, section.

It has been proposed to overcome both difficulties by introduction of auxiliary streams of oxygen suflicient to maintain the flame in a relatively fixed position in the flame chamber, such introduction of auxiliary oxygen being made at the periphery of the flame chamber and immediately downstream from the openings of the gasdistributor, flame-arrester, tubes into the flame chamber, and by having that part of the gas-distributor, flamearrester, section facing the flame chamber in the form of metal conduits surrounding the ends of the tubular channels, in which conduits cooling fluid is circulated, thereby'in effect forming a single pass heat-exchanger.

It has also been proposed to provide a multiplicity of small-bore oxygen ports (orifices) in the metal wall of the heat exchanger facing the flame chamber, the ports being directed at an angle from the vertical such that the streams of oxygen impinge upon the streams of the gaseous mixture of oxygen and methane entering the flame chamber through some but not all of the tubular members. In this proposed arrangement the oxygen supplied to the ports is by way of conduits arranged between groups of the tubular members passing through the cooling chamber of the gas-distributor, arrester section.

While the flame in the flame chamber may be stabilized in either manner, the introduction of auxiliary oxygen provides small localized flame cones of high-heatradiation which considerably increases the radiant heat flux toward the surface of the gas-distributor, flamearrester,.section facing the flame chamber, which radiant heat must be absorbed and dissipated if the flame side of the gas-distributor, flame-arrester, section is to remain intact for any apreciable length of time during operation of the apparatus, whether fabricated of ce ramic material or of metal. Also, and particularly, from the standpoint of commercial production of acetylene from methane and oxygen, provision of simple fluidcirculating metal conduits surrounding the ends of the tubular channels is totally unsatisfactory because of the very high-heat fluxes encountered, which seriously affect the metal surfaces facing the flame chamber, and maintaining the apparatus in satisfactory working condition for any substantial period of time becomes nearly im possible.

During the course of our investigations in the manufacture of unsaturated hydrocarbons, such as acetylene, from gaseous hydrocarbons, such as methane, with oxygen in a flame chamber, and employing a multiplicity of small-bore oxygen ports as described above as a means for providing an auxiliary supply of oxygen to the flame chamber in order to stabilize the flame therein, it was discovered that flame temperatures and radiant heat fluxes were considerably in excess of those heretofore considered normal in the design of such apparatus. In fact, it was found that heat fluxes of the order of 1,180,000 B.t.u./sq. ft./hr., or about 20 times that accepted as practicable in engineering design work, were to be dealt with.

In such circumstance, if the surface of the gas-distributor, flame-arrester, section facing the flame chamber were fabricated from a highly heat-resistant metal alloy, and were water-cooled, the heat radiated to such metallic surface by the main flame and the auxiliary flames in the flame chamber would not be transferred to the water sufliciently rapidly, because of the poor heat conductivity of such metals. The result is that there is a large temperature gradient through the metal wall and thus high internal stresses are generated within the metal, accompanied by comparatively rapid failure, due to cracking at the metal surface adjacent the flame chamber. Accordingly, it is apparent that, if the surface of the gas-distributor, flame-arrester, section facing the flame chamber is of metallic material and a heat exchanger is to be provided around the ends of the gasdistributor tubes entering the flame chamber, either the metal face must be very thin if fabricated from high temperature-resistant alloys, or the face must be made of a relatively more highly heat-conductive metal.

However, in order to have a 'high temperature-resistant alloy conduct the amount of heat encountered, the thickness would be considerably less than practicable for standard fabrication techniques and the mechanical stresses involved.

On the other hand, in such environment, it is apparent that metals having much greater heat conductivity than those metals resistant to high temperatures would by ordinary standards be considered as out of the question as materials of construction, since it would be expected that such metals would quickly be destroyed by the high heat flux by virtue of the fact that, due to the amount of heat to be transferred by the metal, much of the Water circulated in the heat exchanger would be vaporized and little or no liquid would remain in contact with the metallic surface at the face of the gasdistributor, whereby transfer of heat from the metal to the liquid would not take place, but rather the heat transfer would be from metal through vapor to liquid and the good heat-conductive metals would be very rapidly destroyed.

With the knowledge of the heat flux (q/A) involved in the combustion of methane with oxygen to produce acetylene and with the further knowledge that good heat conductivity would be mandatory for the face of the gas-distributor, flame-arrester, section facing the flame chamber, the problem then to be faced is one of transferring this large amount of heat through the metal surfaces of the gas-distributor, flame-arrester, section facing the flame chamber, to the surfaces internally of the heat exchanger to the coolant.

While it is known that a maximum heat flux for a system operating under atmospheric pressure and natural convection velocity is about 380,000 B.t.u./sq. ft./hr., this is still far short of the heat flux involved in the type of apparatus to which the present invention is directed. It was found that in order to absorb a much greater heat flux and still have the temperature gradient through the metal wall facing the flame chamber at a sufliciently low level for practical commercial operation, three factors were critical at any given pressure under which the coolant is circulated in the heat exchanger; the first is the velocity of the body of coolant across the metal surfaces internally of the heat exchanger, the second, subcooling of the coolant (the temperature below the boiling point of the coolant at the pressure at which it is introduced into the heat exchanger), and third, the geometry of the cooling chamber which necessarily bears a relationship to the velocity of the coolant traveling within the cooling chamber of the heat exchanger.

Of the three factors involved, the subcooling of the coolant is the most easily controlled, and it was found during the course of our investigation that in addition to the gas-distributor tubes passing through the heat exchanger, which tubes necessarily act as deflectors for the coolant material, as do the conduits supplying auxiliary oxygen to the oxygen ports, further coolant deflecting members mounted Within the cooling chamber were required and their placement was found to be critical in the sense that such additional coolant deflecting members should form, with the gas-distributor tubes and auxiliary oxygen supply conduits, a plurality of labyrinthine passageways of substantially equal length extending across the cooling chamber from the outer reaches of the cooling chamber to the central portion from which the coolant material is discharged. For example, where the cooling chamber is circular in crosssection, it should be as nearly radially symmetrical as practicable. By designing the apparatus in such a way that these three conditions are met, it was found that the phenomenon of nucleate boiling could be assured substantially uniformly in the cooling chamber of the heat exchanger, and that the heat fluxes involved were readily accommodated by ordinary steel as the material of construction for the end wall of the gas-distributor, flame-arrester, section facing the flame chamber. In this regard, the term nucleate boiling refers to boiling which is initiated at nuclei or tiny centers of active boiling on .a metal surface, such nuclei being induced by minute surface cracks or pits or similar imperfections normally present in the metal surface, with the further provision that the minute bubbles of coolant vapor forming at such nuclei are immediately swept away and condensed in the body of coolant, and thereby prevented from coalescing and forming a blanket of vapor in the vicinity in which boiling is taking place.

One of the objects of the present invention is to provide a suitable design of heat exchanger for the absorption and removal of large amounts of radiant heat through nucleate boiling of a coolant in an apparatus for the production of unsaturated hydrocarbons by the incomplete oxidation of more saturated hydrocarbons with oxygen in a flame reaction.

It is a further object of the present invention to pro vide eflicient heat exchange means in such an apparatus where the apparatus makes provision for introducing a plurality of auxiliary streams of oxygen into the flame chamber to stabilize the flame.

These and other objects of the invention will be apparent to those skilled in the art from the description which follows hereinafter, and particularly with respect to the accompanying drawings attached hereto and made a part hereof.

Pursuant to the above objects, the present invention is directed to an improvement in apparatus for the produc tion of unsaturated hydrocarbons by incomplete oxidation of more saturated hydrocarbons with oxygen in a flame reaction, where such apparatus provides for a mixing chamber for said hydrocarbons and oxygen, a flame chamber into which a plurality of auxiliary oxygen streams are introduced to stabilize the position of said flame, and having a gas-distributor, flame-arrester, section interconnecting said chambers, with provision for a plurality of symmetrically-arranged groups of parallel rows of tubular channels opening into said mixing chamber and said flame chamber, the improvement which includes a double pass, shell-and-tube heat exchanger interposed between said mixing chamber and said flame chamber, said heat exchanger having (a) a first metal tube sheet forming one boundary of said flame chamber, (b) an intermediate baflle substantially coextensive with said first tube sheet and spaced apart therefrom, said bafile having a centrally located perforation therethrough, and (c) a second metal tube sheet spaced apart from said bafile so as to form adjacent fluidly connected cooling chambers, the tubes of said heat exchanger constituting at least a portion of said tubular channels interconnecting said mixing chamber and said flame chamber, ((1) means for introducing coolant into one of said cooling chambers, means for with cooling chamber between said first tube sheet and said' baffie and spaced apart therefrom, said conduits being positioned between adjacent groups of said tubular channels, (f a plurality of hollow metal support members for said conduits, mounted on said first tube sheet and regularly spaced along said conduits in supporting relation thereto, (g) said first tube sheet and said conduits having orifices opening into said hollow support members, the orifices in said first tube sheet being directed toward the space between the openings of adjacent tubular channels into said flame chamber, ,means for introducing oxygen through said conduits, said hollow support members and said orifices, into said flame chamber, (h) metallic coolant deflecting members mounted within said cooling chamber formed by said first tube sheet and said baflle so as to form with said tubular channels and said hollow support members a plurality of labyrinthine passageways of substantially equal length extending across said cooling chamber to said centrally located perforation in said bafile, whereby means are provided to afford substantially uniform nucleate boiling of the coolant in the cooling chamber bounded by said first tube sheet.

In order that those skilled in the art may better understand the principles involved in the present invention, reference may be had to the drawings attached hereto and made a part hereof in which:

FIG. 1 is a composite of sectional plan views of successive quadrants of the cylindrical gas-distributor, flamearrester, section and the shell-and-tube heat exchanger of the apparatus of the present invention, the quadrants being observed at progressively lower levels indicated by A, B, C, and D, respectively, with the tubular channels removed, for clarity, in quadrants A-C, inclusive;

FIG. 2 is an elevation of two vertical sections made from the geometrical center of the apparatus of FIG. 1 to the lines 22 of FIG. 1 and viewed in the direction indicated by the arrows;

FIG. 3 is a vertical section of an oxygen supply conduit taken through a supporting downcomer showing in detail the relationship of the orifices in a conduit and the first tube sheet;

FIG. 4 is a vertical section taken along the axis of one of the conduits and through a downcomer; and

FIG. 5 is a perspective view of a metallic coolant deflecting member placed between the first tube sheet and the baffie so as to complete the generally geometrical symmetry of the labyrinthine passageways.

In the apparatus of the present invention, as shown in detail on the drawings, 4 indicates generally a mixing chamber wherein a hydrocarbon, such as methane, and

oxygen are mixed together, after being preheated, the

gaseous mixture then passing into the gas-distributor, flame-arrester, section 6 through distributor tubes 10 to flame chamber 8. Tubes- 10, through a portion of their length, may be surrounded by suitable insulating or refractory material in the spaces 12. The lower portion of the tubes 10 also form a shell-and-tube type heat exchanger with member 28, which acts as the shell of the heat exchanger, lower metal tube sheet 14 and upper metal tube sheet 16, which may also act as asupport for the insulating or refractory material in spaces 12. The portion of the tubes 10 passing through the heat exchanger may suitably be placed within simple tubular sleeve members (not detailed) extending from upper tube sheet 16 to lower tube sheet 14, although the rate of gas flow through the tubes 10 is sufficiently high that very little cooling of the gas by the heat exchanger is encountered. A bafile plate 18 is interposed between the lower and upper tube sheets 14 and 16, respectively, thereby forming a double pass shelland-tube type heat exchanger, surrounding the ends of the gas-distributor tubes 10 in the region where they enter the flame chamber, and in position to receive heat radiated by the flames in the flame chamber. Mounted upon the lower tube sheet 14 are hollow metal support members 24 for conduits 20, the support members acting as downcomers for carrying the auxiliary supply of oxygen from the conduits 20 through orifices 22 (see detail of FIGS. 3 and 4) into the flame chamber 8 through orifices 26.

The tubes 10 are preferably arranged in groups and in parallel rows in such a manner that their centers fall on a line parallel to a diameter of the heat exchanger and on a line at an angle of 60 to such diameter, the groups consisting three rows of tubes paralleling a diameter of the heat exchanger section, particularly shown in quadrant D of FIG. 1, thus providing triangular pitch arrangement to each group of tubes. The oxygen conduits 20 preferably are placed so as to be interposed between the groups of tubes with the downcomers 24, which also act as coolant deflecting members in the lower cooling chamber, positioned so as to be substantially in register with the symmetrical arrangement of tubular channels 10. In addition, there are provided other metallic coolant deflecting members 30, mounted upon the lower tube sheet 14 and arranged so as to fill out the symmetry of the groups of tubular channels and the downcomers in the outer reaches of the coolant chamber near the inner wall of shell member 28 of the heat exchanger. The coolant deflecting members 30 are preferably of the same crosssectional configuration as the downcomers 24 and tubes 10, shown in FIGS. 1, 2, and 5, as cylindrical. Also, in mounting coolant deflecting members 30 between tube sheet 14 and baflle 18 it is preferred that there be provided a projection which is substantially smaller than the main body of the deflecting member so that such main body is spaced apart from the lower tube sheet to permit the coolant as much access as possible to the heat transfer surface and prevent localized accumulation of vapor, while at the same time retaining the function of the deflecting members.

By such an arrangement of the coolant deflecting members 30, downcomers 24 and tubes 10, in the lower cooling chamber between tube sheet 14 and baffle 18, coolant material circulating in the lower cooling chamber is thereby afforded a plurality of generally equidistant labyrinthine passageways across the cooling chamber, and substantially uniform flow of coolant material from the periphery of the cooling chamber to the centrally located perforation 32 in baflie plate 18 is assured.

The volume rate of flow of the coolant to provide substantially uniform nucleate boiling at the surface of tube sheet 14 is readily estimated for flows of 12-l5 feet per second, taking into account the degree of subcooling of the coolant and the heat flux involved.

Oxygen is supplied to conduits 20 through tubes 34 from oxygen header 36, shown in FIG. 1, and in the preferred embodiment of the apparatus of the present invention, the conduits 20 are arranged between adjacent groups of gas-distributor tubes 10 and downcomers 24 complementing the geometry of the rows of tubes immediately adjacent the oxygen conduits 26.

Water is preferably used as the coolant material, and may be introduced into the cooling chamber formed by the lower tube sheet 14 and bafile 18 through water conduits 38, of which there is preferably more than one, the water :being supplied through header 40, and after passing through openings 38, the water flows through the lower cooling chamber, upwardly through the perforation 32 centrally located in baffle plate 18, and thence around the tubes 10, through the upper cooling chamber formed by the upper tube sheet 16 and baffle 13 and outwardly through a plurality of ports 42, into chamber 44 formed by a innerwall 48 and outerwall 50, and through a second series of ports 46 to a collection chamber not shown. The above-described path of the water circulating in the upper and lower cooling chambers is illustrated by the directional arrows in this portion of the apparatus in FIG. 2, although it will 'be recognized by those skilled in the art that the water may just as effectively be introduced first into the upper cooling chamber flowing through the 4 central orifice and then through the lower cooling cha mher.

In the operation of the apparatus of the present in- .vention to produce acetylene from methane and oxygen, initially the coolant material, preferably water as noted above, for the shell-and-tube heat exchanger is introduced through header 40 to openings 38 and thus into the lower cooling chamber of the heat exchanger toward the centrally located opening 32 in baflie 18, and thus into the upper cooling chamber formed between the upper tube sheet 16 and baflle 18, passing out of the chamber through openings 42, into chamber 44 and finally outwardly through ports 46. A preheated mixture of oxygen and methane is introduced into mixing chamber 4, the amount of oxygen in the mixture being less than about one-third of the stoichiometric amount required for complete oxidation of the methane to carbon dioxide and water, the mixture then passing through distributor tubes at such a rate of flow as to be in excess of the flame propagation of the flames in flame chamber 8. The mixture of oxygen and methane passing into flame chamber 8 is ignited by a suitable pilot light (not shown) and oxygen is fed through header 36, and tubes 34 into conduits 20 from which is passes into downcomers 24 and outwardly into the flame chamber through orifices 26 which direct the streams of auxiliary oxygen between pairs of tubular conduits 10 adjacent the orifices, thus generating auxiliary high temperature, small localized flame cones in the flame chamber, assuring stabilization of the main, lower temperature, acetylene generating flame generated by the mixture of oxygen and methane, passing through those distributor tubes not adjacent to the auxiliary oxygen orifices 26.

In regard to the coolant material, preferably water, and with the first tube sheet 14 fabricated of ordinary steel or equally good heat conductor, the volume rate of flow of the water, and the temperature of the water introduced into the heat exchanger, should be such as to insure substantially uniform nucleate boiling of the water in the lower cooling chamber of the heat exchanger, i.e., the

volume rate of flow should be such as to sweep away the minute bubbles of steam as they are formed on the metal surfaces of the heat exchanger, particularly on the lower tube sheet 14, and the water should be sufficiently subcooled to insure absorption of the bubbles of steam in the main body of liquid. In this respect, it has been found specifically that, where gas-distributor, flame-arrester, section is circular in cross-section and the area of the tube sheet exposed to the flames in the flame chamber is of the order of eight-tenths of one square foot (0.8 sq. ft), and the water entering the cooling chamber is subcooled to a temperature at least 100 below its boiling point at the pressure existing in the lower cooling chamber, substantially uniform nucleate boiling is assured if the volume rate of flow is sufficient to provide movement of the body of water at a speed of about twelve feet per second along the labyrinthine passageways formed by the tubes 10, conduits 20, downcomers 24, and coolant deflecting members 30, as the water passes from the outer reaches of the groups of tubes toward the centrally located perforation 30 in baflle plate 18.

Further, it has been found that without assuring nucleate boiling substantially uniformly in the lower cooling chamber of the heat exchanger, by designing this part of the apparatus so that there the water has substantially unequal paths of flow across the lower tube sheet of the cooling chamber, the formation of relatively'large localized bodies of steam on the lower tube sheet are encountered, thereby considerably lessening the heat exchange capacity of the lower tube sheet, and thereby promoting localized stresses in metal in this portion of the heat exchanger, which stresses in turn result in failure of the metal in these areas, rendering the apparatus inoperable.

8 It is to be understood that although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited, since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

What is claimed is:

1. In an apparatus for the production of unsaturated hydrocarbons by incomplete oxidation of more saturated hydrocarbons with oxygen in a flame reaction, such apparatus having a mixing chamber for said hydrocarbons and oxygen, a flame chamber into which a plurality of auxiliary streams of oxygen are introduced to stabilize said flame, and a gas-distributor, flame-arrester, section interconnecting said chambers and having a plurality of parallel rows of tubular channels opening into said mixing chamber and said flame chamber, the improvement which includes:

(1) a double pass shell-and-t'ube heat exchanger interposed between said mixing chamber and said flame chamber, said heat exchanger having a shell surrounding,

, (a) a first metal tube sheet forming one boundary of said flame chamber,

(b) an intermediate baffle coextensive with said first tube sheet and spaced apart therefrom, said baflle having a centrally located perforation therethrough, and

(c) a second metal tube sheet spaced apart from said bafllle so as to (form adjacently fluidly connected cooling chambers, the tubes of said heat exchanger constituting at least a portion of said tubular channels interconnecting said mixing chamber and said flame chamber,

(d) means for introducing coolant into one of said cooling chambers, means for withdrawing coolant from the other of said cooling chambers,

(2) said mixing chamber, said flame chamber, and said shell-and-tube heat exchanger being positioned coaxially and vertically,

(3) a plurality of conduits mounted within said cooling chamber, between said first tube sheet and said baflle and spaced apart therefrom, said conduits being positioned between adjacent groups of said tubular channels,

(a) a plurality of hollow support members for said conduits mounted on said first tube sheet and regularly spaced along said conduits in supporting relation thereto,

(b) said first tube sheet and said conduits having orifices opening into said hollow support members, the orifices in said first tube sheet being directed between the openings of adjacent tubular channels into said flame chamber, means for introducing oxygen through said conduits, said hollow sup-port members, and said orifices into said flame chamber,

(0) said tubular channels being arranged in parallel rows such that their centers fall on a line parallel to a diameter of said heat exchanger and the line at an angle of 60 to such diameter,

(4) coolant deflecting members mounted within said cooling chamber formed by said first tube sheet and said baffle so as to form with said tubular channels and said hollow support members a plurality of labyrinthine passageways of substantially equal length extending across said cooling chamber to said centrally located perforation in said b-aflle, said hollow support members together with said cooling deflecting members being positioned on said first wall of said cooling chamber in such a manner as to retain the symmetry of said groups of tubular channels.

2. The apparatus in claim 1 wherein said tubular chan- 11615 a e arra ged in groups of three parallel rows such and said coolant deflecting members extend from said first tube sheet to said bafile and have -a projection extending from the main body of said member to the lower tube sheet, such projection being substantially smaller in diameter than said main body.

References Cited by the Examiner UNITED STATES PATENTS 1,917,595 7/1933 McDermet 165-161 X FOREIGN PATENTS 520,578 12/ 195 3 Belgium.

MORRIS O. WOLK, Primary Examiner.

I. H. TAYMAN, JR., Assistant Examiner. 

1. IN AN APPRATUS FOR THE PRODUCTION OF UNSATURATED HYDROCARBONS BY INCOMPLETE OXIDATION OF MORE SATURATED HYDROCARBONS WITHOXYGEN IN A FLAME REACTION, SUCH APPARATUS HAVING A MIXING CHAMBER FOR SAID HYDROCARBONS AND OXYGEN, A FLAME CHAMBER INTO WHICH A PLURALITY OF AUXILIARY STREAMS OF OXYGEN ARE INTRODUCED TO STABILIZE SAID FLAME, AND A GAS-DISTRIBUTOR, FLAME-ARRESTER, SECTION INTERCONNECTING SAID CHAMBERS AND HAVING A PLURALITY OF PARALLEL ROWS OF TUBULAR CHANNELS OPENING INTO SAID MIXING CHAMBER AND SAID FLAME CHAMBER, THE IMPROVEMENT WHICH INCLUDES: (1) A DOUBLE PASS SHELL-AND-TUBE HEAT EXCHANGER INTERPOSED BETWEEN SAIDMIXING CHAMBER AND SAID FLAME CHAMBER, SAID HEAT EXCHANGER HAVING A SHELL SURROUNDING, (A) A FIRST METAL TUBE SHEET FORMING ONE BOUNDARY OF SAID FLAME CHAMBER, (B) AN INTERMEDIATE BAFFLE COEXTENSIVE WITH SAID FIRST TUBE SHEET AND SPACED APART THEREFROM, SAID BAFFLE HAVING A CENTRALY LOCATED PERFORATION THERETHROUGH, AND (C) A SECOND METAL TUBE SHEET SPACED APART FROM SAID BAFFLE SO AS TO FORM ADJACENTLY FLUIDLY CONNECTED COOLING CHAMBERS, THE TUBES OF SAID HEAT EXCHANGER CONSTITUTING AT LEAST A PORTION OF SAID TUBULAR CHANNELS INTERCONNECTING SAID MIXING CHAMBER AND SAID FLAME CHAMBER, (D) MEANS FOR INTRODUCING COOLANT INTO ONE OF SAID COOLING CHAMBERS, MEANS FOR WITHDRAWING COOLANT FROM THE OTHER OF SAID COOLING CHAMBERS, (2) SAID MIXING CHAMBER, SAID FLAME CHAMBER, AND SAID SHELL-AND-TUBE HEAT EXCHANGER BEING POSITIONED COAXIALLY AND VERTICALLY, (3) A PLURALITY OF CONDUITS MOUNTED WITHIN SAID COOLING CHAMBER, BETWEEN SAID FIRST TUBE SHEET AND SAID BAFFLE AND SPACED APART THEREFROM, SAID CONDUITS BEING POSITIONED BETWEEN ADJACENT GROUPS OF AID TUBULAR CHANNELS, (A) A PLURALITY OF HOLLOW SUPPORT MEMBERS FOR SAID CONDUITS MOUNTED ON SAID FIRST TUBE SHEET AND REGULARLY SPACED ALONG SAID CONDUITS IN SUPPORTING RELATION THERETO, (B) SAID FIRST TUBE SHEET AND SAID CONDUITS HAVING ORIFICES OPENING INTO SAID HOLLOW SUPPORT MEMBERS, THE ORIFICES IN SAID TUBE SHEET BEING DIRECTED BETWEEN THE OPENINGS OF ADJACENT TUBULAR CHANNELS INTO SAID FLAME CHAMBER, MEANS FOR INTRODUCING OXYGEN THROUGH SAID CONTUITS, SAID HOLLOW SUPPORT MEMBERS, AND SAID ORIFICES INTO SAID FLAME CHAMBER, (C) SAID TUBULAR CHANNELS BEING ARRANGED IN PARALLEL ROWS SUCH THAT THEIR CENTERS FALL ON A LINE PARALLEL TO A DIAMETER OF AID HEAT EXCHANGER PARALLEL TO A DIAMETER OF SAID HEAT EXCHANGER AND THE LINE AT AN ANGLE OF 60* TO SUCH DIAMETER, COOLING CHAMBER FORMED BY SAID FIRST TUBE SHEET AND SAID BAFFLE SO AS TO FORM WITH SAID TUBULAR CHANNELS AND SAID HOLLOW SUPPORT MEMBERS A PLURALITY OF LABYRINTHINE PASSAGEWAYS OF SUBSTANTIALLY EQUAL LENGTH EXTENDING ACROSS SAID COOLING CHAMBER TO SAID CENTRALLY LOCATED PERFORATION IN SAID BAFFLE, SAID HOLLOW SUPPORT MEMBERS TOGETHER WITH SAID COOLING DEFLECTING MEMBERS BEING POSITIONED ON SAID FIRST WALL OF SAID COOLING CHAMBER IN SUCH A MANNER AS TO RETAIN THE SYMMETRY OF SAID GROUPS OF TUBULAR CHANNELS. 